1. Field of the Invention
The present invention relates generally to lithographic methods employed for fabricating microelectronic fabrications. More particularly, the present invention relates to charged particle beam lithographic methods employed for fabricating microelectronic fabrications.
2. Description of the Related Art
Microelectronic fabrications are formed from microelectronic substrates over which are formed patterned microelectronic conductor layers which are separated by microelectronic dielectric layers. In the process of forming patterned microelectronic conductor layers within microelectronic fabrications, as well as in the process of forming other types of patterned microelectronic layers within microelectronic fabrications, further as well as in the process of forming patterned masking layers within photomasks which may be employed for forming patterned microelectronic layers of various varieties within microelectronic fabrications, there may be employed direct lithographic writing methods, such as but not limited to direct electron beam lithographic writing methods. Such direct lithographic writing methods may be employed to form within a blanket resist layer a latent exposed pattern which upon subsequent development provides a patterned resist mask for: (1) etching within a microelectronic fabrication a blanket microelectronic layer formed beneath the patterned resist mask to form a patterned microelectronic layer formed beneath the patterned resist mask; or in the alternative (2) etching within a photomask a blanket masking layer formed beneath the patterned resist mask to form a patterned masking layer formed beneath the patterned resist mask.
While direct lithographic writing methods, such as in particular direct electron beam lithographic writing methods, are thus desirable within the art of microelectronic fabrication for forming patterned resist layers which are employed either directly or indirectly for forming patterned microelectronic layers within microelectronic fabrications, direct lithographic writing methods, and in particular direct electron beam lithographic writing methods, are nonetheless not entirely without problems in the art of microelectronic fabrication for forming patterned resist layers which are employed either directly or indirectly for forming patterned microelectronic layers within microelectronic fabrications.
In that regard, it is known in the art of microelectronic fabrication that, in particular, electron beam exposed directly written and subsequently developed patterned resist layers are often difficult to form with enhanced pattern fidelity and enhanced critical dimension uniformity encompassing various areal densities of patterned resist layers within microelectronic fabrications insofar as, in particular, electron beam radiation when employed for directly forming patterned resist layers within microelectronic fabrications scatters from either within a blanket resist layer which is directly exposed while employing electron beam radiation (i.e., forward scattering), or in the alternative electron beam radiation also scatters from a substrate over which is formed a blanket resist layer which is directly exposed employing electron beam radiation (i.e., back scattering). Such forward scattering or back scattering leads to pattern density related in homogeneity effects, such as pattern fidelity in homogeneity effects and critical dimension uniformity in homogeneity effects, such in homogeneity effects generally known in the art of microelectronic fabrication as proximity effects.
It is thus desirable in the art of microelectronic fabrication to provide methods and materials through which there may be attenuated proximity effects when exposing a blanket resist layer while employing a charged particle beam method, and in particular an electron beam method, in the process of forming from the blanket resist layer a patterned resist layer, such that a patterned microelectronic layer formed while employing the patterned resist layer as an etch mask may similarly also be formed with enhanced pattern fidelity and enhanced critical dimension uniformity.
It is towards the foregoing objects that the present invention is directed.
Various methods have been disclosed in the art of microelectronic fabrication for forming, with desirable properties, patterned resist layers for use when fabricating microelectronic fabrications.
Included among the methods, but not limiting among the methods, are methods disclosed within: (1) Meiri et al., in U.S. Pat. No. 5,241,185 (an electron beam exposure method which employs a determination of an electron beam radiation dose with respect to a contracted electron beam exposed resist layer pattern having a negative bias with respect to desired developed resist layer pattern); (2) Kanata, in U.S. Pat. No. 5,667,923 (a charged particle beam exposure method which employs a determination of a backscattered charged particle beam density from a patterned substrate layer over which is formed a blanket resist layer which is desired to be exposed while employing the charged particle beam exposure method); (3) Kim, in U.S. Pat. No. 5,804,339 (an electron beam radiation exposure method which employs a separate electron beam exposure for purposes of correcting for an optical proximity effect); (4) Ohnuma, in U.S. Pat. No. 5,885,748 (an electron beam exposure method which employs corrections for both self proximity effects and mutual proximity effects when exposing a blanket resist layer while employing the electron beam exposure method); and (5) Tzu et al., in U.S. Pat. No. 5,994,009 (an electron beam exposure method which provides for correction of both optical proximity effects and process related proximity effects, such as topographic process related proximity effects, when exposing a blanket resist layer while employing the electron beam exposure method).
Desirable within the art of microelectronic fabrication are additional methods and materials through which there may be attenuated proximity effects when exposing a blanket resist layer while employing a charged particle beam method, and in particular an electron beam method, in the process of forming from the blanket resist layer a patterned resist layer, such that a patterned microelectronic layer formed while employing the patterned resist layer as an etch mask may similarly also be formed with enhanced pattern fidelity and enhanced critical dimension uniformity.
It is towards the foregoing objects that the present invention is directed.